ABSTRACT Increasing the use of nitrogen (N) fertilizers will be necessary to enhance grain and pasture yields to satisfy the growing world demand for food. Organic amendments, such as farm dairy effluents (FDE), are an alternative to traditional synthetic fertilizers. However, part of the applied N could be lost as ammonia (NH3) volatilization or nitrous oxide (N2O) emission, decreasing N availability to plants. Nitrification inhibitors, such as dicyandiamide (DCD), suppress the microbial process of nitrification, decreasing soil nitrate concentration and, therefore, N2O emission. Reducing N2O losses from agricultural soils is a key subject for sustainable production. This research aimed to quantify the effect of DCD addition to the FDE on the emissions of N2O and the volatilization of NH3 from the soil. A field trial was carried out in which NH3 volatilization and N2O emission were measured over 49 days after applying FDE, FDE with DCD (DCD), and control (C, without N added) treatments. The amount of N applied as FDE was 120 kg of N ha-1. Accumulated N2O emission during the 49 days after the application was 526, 237, and 174 g N2O-N ha-1 from the soil in the FDE, DCD, and C treatments, respectively. No significant differences were observed in accumulated NH3 volatilization. Pasture yield was higher in DCD treatment, followed by C and FDE. Under low temperatures and high soil moisture conditions, adding DCD to the FDE could be considered an effective alternative to increase pasture yields, decrease N2O emissions, and maintain NH3 volatilization, reducing total N losses to the atmosphere by about 14 %. Adding DCD to the FDE is a promising alternative for the more efficient N use of farm dairy effluents as fertilizer to mitigate N losses, tending to reduce N losses as N2O emissions. More studies are necessary to verify the result of using FDE + DCD under different soils and climates. (N food amendments , (FDE) However NH (NH3 NO O (N2O plants inhibitors (DCD) nitrification therefore production 4 C, (C added treatments 12 ha1. ha1 ha 1. 1 526 237 17 N2ON NON ha- respectively treatment conditions % climates (FDE (NH (DCD 52 23 ON 5 2

RESUMEN El aumento de las fuentes de fertilización será necesario para satisfacer la creciente demanda de alimentos en todo el mundo. Por este motivo, las enmiendas orgánicas surgen como una alternativa a los fertilizantes sintéticos. El compostaje de residuos orgánicos estabiliza el contenido de nitrógeno (N) y retrasa la liberación de N al suelo. La aplicación de enmiendas compostadas al suelo podría reducir las pérdidas de N, incluido el óxido nitroso (N2O), un gas de efecto invernadero con gran potencial de calentamiento global. El objetivo de este trabajo fue evaluar la emisión de N2O desde un suelo Argiudol típico luego de aplicar un fertilizante sintético tradicional, guano de ave crudo y compostado y un suelo control. Las tasas emisión de N2O acumuladas durante los 32 días que duro el ensayo fueron 1273, 965, 423 y 244 g de N2O-N ha-1 desde el suelo con aplicación de urea, guano de ave, compost de guano de ave y control, respectivamente. Nuestros resultados sugieren que la aplicación de compost de guano al suelo produce menores emisiones de N2O que la aplicación de guano de ave crudo o de urea. La presencia de compuestos más estabilizados en el compost de guano disminuye la disponibilidad de nitrato del suelo.

ABSTRACT Diversification in fertilizer sources will be necessary to meet the growing demand for food worldwide. For this reason, organic amendments emerge as a synthetic fertilizers alternative. Composting organic waste stabilizes the nitrogen (N) content and delays N release to the soil. Applying composted amendments to the soil could reduce the losses of N, including nitrous oxide (N2O), a greenhouse gas with great potential for global warming. The objective of this work was to evaluate the N2O emission in typical Argiudol soil after applying a traditional synthetic fertilizer, raw poultry manure, composted poultry manure and control soil. Cumulative N2O emission rates during the 32 days of the trial were 1273, 965, 423, and 244 g N2O-N/ha-1 from the soil using urea, poultry manure, composted poultry manure, and control, respectively. Our results suggest that the application of composted poultry manure to the soil produces lower N2O emissions than the application of raw poultry manure or urea. The presence of more stabilized compounds in the composted manure decreases the soil nitrate availability.

ABSTRACT Nitrous oxide (N2O) is a greenhouse gas that contributes substantially to global climate change. The N2O soil emissions have a large uncertainty because of its low atmospheric concentration levels and enormous spatial and temporal variability, which hinders its correct field measurement. For this reason, there are many papers focused on improving the N2O measurements in the field, which focus on different parts of the measurement process. However, no studies have focused on determining the appropriate method, in terms of simplicity and precision, for the sample extraction from inside of the chambers and its transfer to the storage vials, although this step is key in the sampling process. This study aimed to assess and compare the accuracies of three simple and economical methods in transfer soil emitted N2O from inside of the chambers to the vials. For this, a highly accepted method (vacuum by manual pump) and two simpler alternative methods (gas exchange by displacement and vacuum by syringe) were compared. Thirty static chambers were assessed with the quantified N2O emission values varied from 0 to 450 µg m-2 h-1 of N-N2O. Out of the three assessed methods, the vacuum method through the use of a manual vacuum pump was the best to quantifying N2O soil emissions (capturing 57 % of the highest emission values), followed by the gas exchange method by displacement (30 %), and finally by the vacuum method by syringe extraction (13%).

The objective of this work was to compare the effect of the application of different sources of phosphorus and sulfur (synthetic fertilizers, phosphate rock and gypsum) on soybean crop, and to evaluate the residuality of these nutrients according to the source of application in a typical Argiudol soil under no tillage system. The results obtained show that the fertilization with a mixed of phosphate rock and gypsum, allowed to obtain the same yields as the traditional fertilization. However, no residual effect of the phosphate rock on the soil extractable phosphorus and sulfur was measured.

El presente trabajo tuvo como objetivos comparar el efecto de la aplicación de diferentes fuentes de fósforo y azufre (fertilizantes sintéticos, roca fosfórica y yeso) sobre el rendimiento del cultivo de soja, y evaluar la residualidad de estos nutrientes según la fuente de aplicación en un suelo Argiudol típico bajo siembra directa. Los resultados obtenidos muestran que la fertilización combinada con roca fosfórica y yeso permitió obtener los mismos rendimientos que la fertilización tradicional. Sin embargo, no se encontró un efecto de residualidad del fósforo extractable y azufre medidos en el suelo asociado a las fuentes menos solubles.

The fruit of the pecan tree, Carya illinoensis Koch, is considered a very healthy food. In Argentina, pecan cultivation has been expanding rapidly but very little research has been conducted on pecan fertilization and planting systems. The objectives of this study were to characterize some physical-chemical and chemical properties in a pecan crop, and compare different basal fertilization (FB) treatments under two high density plantation frames (MP). Plantation was conducted in Villanueva (Buenos Aires province), on a Tapthoargic Hapludoll, with 10 x 10 m frames (real part: MR) and 8 x 8 m frames (staggered: TR). The experimental design was a split plot with four replications. The main plots were the two frames and the subplots were the different fertilization treatments: Compost (C), Phosphorus (P), slow release Nitrogen (N), and an unfertilized control (T). The determinations to assess the growth of pecan plants were: plant height and stem diameter. With regard to soil fertility, phosphorus fertilization and the addition of compost significatively increased the levels of Bray-P. The organic fertilizer treatment (compost) showed a significant increase in the height of the pecan plantation under the 8 x 8 m frame, which was not apparent in any case for the stem diameter, with a MP x FB significant interaction (P = 0.01) for height variation in the first year. The plantation frame with or without basal fertilization had no effect on pecan volume during the study period.

El pecán, Carya illinoensis Koch, es una especie cuyo fruto es reconocido como un alimento altamente saludable. Su cultivo se encuentra en expansión en la Argentina pero existen muy pocas investigaciones sobre fertilización y sistemas de plantación. Los objetivos del trabajo fueron caracterizar algunas propiedades físico-químicas y químicas de un suelo en el que se inicia un cultivo de pecán, y comparar tratamientos de fertilización de base (FB) en dos marcos de plantación de alta densidad (MP). Se realizó una plantación de pecán en Villanueva (provincia de Buenos Aires), sobre un suelo Hapludol taptoárgico, con dos marcos de plantación: 10 x 10 m (marco real: MR) y 8 x 8 m (tresbolillo: TR). El diseño del experimento fue en parcelas divididas con cuatro repeticiones. La parcela principal fueron los dos marcos de plantación, y las subparcelas fueron los distintos tratamientos de fertilización base: Compost (C), Fósforo (P), Nitrógeno (N) y Control sin fertilización base (T). Las determinaciones para evaluar el crecimiento de las plantas de pecán fueron: la altura de las plantas y el diámetro del tronco. Con respecto a la fertilidad del suelo, la fertilización fosforada y el agregado de compost permitieron aumentar significativamente los niveles de P-Bray. El tratamiento con fertilización orgánica: compost, presentó un incremento significativo en altura de los pecanes en el marco de plantación 8 x 8 m, que no se manifestó en ningún caso en los diámetros del tronco, con una interacción MP x FB significativa (P=0,01) para la variación de altura al primer año. La variación del volumen del árbol durante el año de experimentación no presentó efectos significativos según el marco de plantación ni la fertilización base aplicada.